The only colouring option that is available for the Web Client is to show Bookings by the assigned Project Colour in the fw Desktop app.
Go to Edit Project window > Eye menu > Force Colour.
If you've chosen in Toolbox > Settings > Hourline > Show Bookings > Project Colour/Client colour, they will show up in the selected Colour in the Hourline.
In Toolbox > Settings > Server Setup > tick: Show Project Colours For Events In The Web Client.
The Bookings will show in the Web Client with the chosen Project Colour.